Hey, remember that guy we caught a glimpse of at the end of The Avengers credits; the one who shot us a sly purple smile? This guy:

Though we haven’t seen him in any Guardians of the Galaxy footage as yet, The Latino Review reports that director James Gunn has discussed a particular Thanos scene (could be considered spoilerish, so swipe if you want to read: “He’s the main sort of… He works with Ronan (Lee Pace). In my movie Ronan works for Thanos, and Ronan is the main bad guy in our film.” The LR also reports Gunn spoke of Thanos on a rocket throne in act 3. End spoiler.

Multiple outlets have confirmed Thanos will be voiced by Josh Brolin, both in Guardians and Avengers: Age of Ultron (it is unknown whether Brolin will later take on motion capture for AAoU, but rumor has it his role will be more prominent).